Anonymous
There should be no issue using an embedded SRT subtitle with your mp4s.
I routinely add/embed SRT subtitles to my mp4 files using ffmpeg and they display fine using the Roku Media Player (RMP) via USB on my Ultras or through DLNA on my servers. I usually just use toggleable ones (able to turn on and off), but burnt-in SRT files also works fine.
With Roku, 'Closed Captioning' is the same as 'Subtitles' as far as toggling them on/off. (used interchangeably). When playing the content, press the asterisk (*) button on your Roku remote and under 'Closed Captioning', select "Always On".
You can also set Closed Captioning (Subtitles) to always be on under Settings/Accessibility/Captions Mode/ [Always On].
The above Captions submenu also allows you to change the Captions formatting under 'Captions Style' (ie. change color, size, opacity, etc)
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I only use SRT nowadays, but I do have notes in my compiling that SRT, VTT, and ASS seemed to work in mp4 files on Roku, while only SRT and VTT worked in mkv files with Roku. I vaguely recall that Roku does not support Image-Based subtitles. Roku used to have a Support Article with their supported closed captioning/subtitle formats but looks like it has been removed. (or I am having trouble finding it).
I do believe it used to be provided in this Support Article listing the other formats. (How to use Roku Media Player to play your videos, music and photos)
Sometimes users will run into issues when using Plex or Emby or other server software regarding subtitles, but those are usually just settings or bugs. Should really not be having an issue if just using Roku Media Player though.
Thanks for that yes have tried the settings you referred to
Anonymous
Are you using any server software that may have an additional subtitle setting? Maybe try enabling or disabling it and see if Roku can now play the subtitle track.
Since it is seeing it, something is precluding it from playing. Sometimes just restarting the server and the Roku device (Settings/System/Power/System Restart or Settings/System/System Restart) may refresh and clear out any miscommunication between the two.
I will note though that when I have had issues with Roku Media Player, it did seem to affect my mp4 files more than it did with my mkv files. Currently, though, I am not seeing any issues with subtitles and I had just tested both an embedded SRT and and an embedded burnt-in SRT file before posting the previous reply. (didn't see any issues).
The Roku Streaming Sticks (2025 models) are brand new so it is possible there may be an issue that needs to be looked at by Roku but would have to rule out server culprits first.
